Understanding of T cell activation and costimulatory mechanisms have led to the identification of novel molecular targets for the treatment of various immunological disorders. Since costimulatory pathways are considered to be essential for T cell activation and differentiation, manipulating co-stimulatory signals on antigen encountered T cells has been considered as an attractive approach for inducing antigen specific tolerance. Two approaches are well adopted in inducing tolerance. Firstly, disrupting T cell activation using blocking antibodies or soluble receptors has often induced tolerance to antigens. Second approach is through exploiting the signaling of T cell negative regulators. Negative regulators that are upregulated significantly on activated T cells have been the molecules of attention in last several years. CTLA-4, PD-1 and BTLA are the three major T cell negative regulators identified and explored as the targets for inducing T cell tolerance. There are other ligands with unknown negative regulators on activated T cells. Induction of antigen specific tolerance depends on concurrent engagement of the T cell receptor (TCR) and these negative regulators. We and others have successfully demonstrated this both in vitro and in vivo. Designing flexible and effective system for this co-ligation is the next step towards achieving the goal of using costimulatory control as antigen specific tolerance induction strategy for clinical use. Our hypothesis is that engaging multiple negative regulators on T cells along with TCR on antigen specific T cells will be necessary and sufficient to induce effective antigen specific tolerance. We propose to generate injectable biodegradable microspheres coated with recombinant MHC-peptides and ligands of T cell negative regulators as tolerogenic antigen presenting system to induce antigen specific T cell tolerance. This study will be aimed at: 1) testing the potential of microsphere bound MHC-dimer peptide complex and negative regulatory ligands in inducing effective antigen specific tolerance using TCR-transgenic mice, and 2) exploring the potential of tolerogenic microsphere based antigen presenting system in preventing and treating autoimmune diabetes using NOD mouse model. The results from this study will help us design an effective antigen specific immunotherapeutic approach that can be used to treat or prevent autoimmune diseases, like childhood type 1 diabetes and other immune mediated disorders through tolerance induction and regulatory T cell induction. [unreadable] [unreadable] [unreadable] [unreadable]